RESUMO
OBJECTIVE: To investigate the effects of Astragalus polysaccharide (APS) on the expressions of apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1) and thioredoxin (TRX) in MRC-5 human embryo lung fibroblasts induced by hydrogen peroxide (H2O2) and explore the mechanism of APS protecting MRC-5 cells from oxidative damage. METHODS: The MRC-5 cells were randomly divided into groups: the normal control group, groups induced by H2O2 of different concentrations, groups treated with 200, 400, 800 mg/L APS. The inhibitory rate of cell proliferation in H2O2-induced MRC-5 cells was measured by MTT assay to make sure the successful establishment of oxidative damage model. With the optimal concentration of H2O2 and different concentrations of APS on MRC-5 cells, we determined the optimal concentrate of APS to prevent oxidative damage in MRC-5 cells. The level of 8-hydroxy-2'-deoxyguanosine (8-OHdG) was detected by immunofluorescence staining. The apoptotic cells were identified by flow cytometry (FCM). The mRNA and protein levels of APE/Ref-1 and TRX were respectively detected by reverse transcription PCR and Western blotting. RESULTS: H2O2 induced oxidative damage in MRC-5 cells in a concentration-dependent manner. We chose the oxidative damage model induced by 800 µmol/L H2O2 for 24 hours to further study the protective mechanism of APS. Compared with H2O2 control groups, 200 mg/L APS significantly increased the protein level of APE/Ref-1 and TRX, decreased the content of 8-OHdG and the apoptosis of MRC-5 cells, and improved dramatically the cell viability. CONCLUSION: H2O2 can induce oxidative damage in MRC-5 cells. APS can promote APE/Ref-1 and TRX expressions in the damaged MRC-5 cells to relieve the oxidative damage and inhibit cell apoptosis.
